This invention relates to a series of embodiments which protect the back chamber seals in a scroll compressor if the scroll compressor is inadvertently run in reverse.
In the prior art, scroll compressors are becoming widely utilized in refrigerant compression applications. There are a number of reasons why scroll compressors are preferred compared to other compressor types, and these reasons have led to their wide adoption. However, scroll compressors do present a number of design challenges.
Scroll compressors have an orbiting scroll moving relative to a fixed scroll to decrease the size of compression chambers and compress entrapped fluid. As fluid is compressed between the scroll wraps, a separating force is generated tending to force the orbiting scroll away from the fixed scroll both axially and radially.
The prior art taps a working pressure compressed fluid to a chamber behind the orbiting scroll to act in opposition to the axial separating force. The back pressure fluid biases the orbiting scroll axially against the fixed scroll. Typically, a pair of seals are placed in grooves on either side of a back pressure tap to seal and define the area of the back chamber. This type arrangement works well to provide a back pressure force in opposition to the separating force from the compressed fluid.
There have been challenges to maintaining the back chamber systems. In particular, scroll compressors have sometimes been inadvertently run in reverse. When this happens, the scroll members quickly generate heat, which is conducted to the seals. Reverse rotation may occur upon set up of the scroll compressor if the electronics are improperly connected. As an example, when a three phase power supply is miswired there may be reverse rotation. Also, a power flicker can cause reverse running in compressors equipped with single phase motors.
The seals expand due to this heat causing the inner seal to seal against the outer diameter wall of the seal groove. The expanded seal then blocks communication of suction pressure from outside the back chamber into the back chamber.
Typically, the back chamber is at a working pressure above suction pressure when the scroll compressor is rotating in the proper direction. However, upon inadvertent reverse rotation, the opposite is true. In fact, the pressure communicating to the back pressure chamber is lower than suction, as the compressor is effectively acting as a vacuum pump.
When the suction pressure is greater than the pressure in the back chamber and the inner seal OD seals against the groove wall, the pressure imbalance crushes the lower lip against the upper lip. This is true since the seals block communication of suction pressure into the back chamber. The imbalance between the very low pressure in the back chamber and the suction pressure has thus led to the seals being crushed, thus preventing the seals from sealing during normal operation.